1. Field of the Invention
The present invention relates to an airframe panel for aircraft used primarily for an aircraft wing.
2. Description of the Related Art
An aircraft main wing is formed by attaching an aircraft wing panel forming the outer surface of the main wing to a frame member forming a skeleton. The aircraft wing panel is curvedly formed into a three-dimensional shape. Specifically, in an airframe, for example, one in which an engine is attached to the lower part of the main wing, the aircraft wing panel forming the upper surface of the main wing is curvedly formed so that the outer surface side of the main wing is convex in the spanwise direction of the wing, and the aircraft wing panel forming the lower surface of the main wing is curvedly formed so that the outer surface side of main wing is concave in the spanwise direction of the wing (convex upwardly).
The main wing constituted by such aircraft wing panels includes stringers and ribs to secure the strength (see Japanese Patent Laid-Open No. 2011-51517 and Japanese Patent Laid-Open No. 2012-171453). The stringers are provided on the inner surface of the main wing along the spanwise direction of the wing, and the ribs are provided along the chordwise direction of the main wing. An example of the configuration is shown in FIG. 7. In this example, a plurality of stingers 115 are formed on the inner surfaces of an upper skin 111 and a lower skin 113 to extend in the spanwise direction (the direction perpendicular to the drawing of FIG. 7) of a main wing 100 between a front and a rear (in the horizontal direction in the drawing of FIG. 7) of the main wing 100. The stringers 115, along with front and rear spars (not shown), transmit forces such as bending and torsional forces which act on the main wing 100 in the longitudinal direction, the spanwise direction, and vertical direction, to an aircraft fuselage to which the main wing 100 is attached. On the other hand, ribs 117 extend in the chordwise direction of the main wing 100, and are provided across the upper skin 111 and the lower skin 113.
The lower skin 113 generally includes thick-walled portions 113b along the roots of the stringers 115 to secure the required rigidity and the like, and thin-walled portions 113a as the remainder thereof in order to reduce the weight of the main wing. The rib 117 includes steps at its edge 117a, which is to be attached to the lower skin 113, so as to conform to the thin-walled portions 113a and thick-walled portions 113b of the lower skin 113.